1. Field of the Invention
The present invention relates to a technology for controlling safety message transmission between group driving vehicles, and more particularly, to a system and a method for controlling safety message transmission between group driving vehicles capable of ensuring the reliability of emergency safety message transmission/reception as a vehicle having received an emergency safety message transmits a general safety message based on adjusted transmission power and adjusted transmission time interval.
2. Discussion of Related Art
Recently, studies on smart vehicles have progressed in various aspects, and methods for improving road efficiency and fuel efficiency together with smart vehicles capable of performing unmanned autonomous driving are also being studied.
Rapid development of smart transportation systems is accelerating as infrastructure technology such as various kinds of sensors and communication devices applied to vehicles starts to be developed in complement thereto and integrated.
Smart vehicles in which various sensors and wireless communication functions are installed to recognize a situation and prevent traffic accidents or provide a variety of transportation information and data services to a driver have several features.
First, in smart vehicles, a plurality of vehicle sensors (Rada, light detection and ranging (Lidar), cameras, etc.) are installed, and convenience and safety functions for drivers are provided by recognizing distances between vehicles, lanes, etc.
Further, since smart vehicles support various wireless communication protocols (Long Term Evolution (LTE), WAVE, wireless fidelity (Wi-Fi), Bluetooth (BT), etc.), network services are able to be provided anywhere and at any time.
Moreover, such smart vehicles support gateway and routing functions supporting different types of wireless data transmission and reception, support single autonomous driving and group driving functions, and transmit and receive various safety messages.
Technology for increasing road efficiency per unit area and improving fuel efficiency of vehicles through group driving in which a plurality of vehicles are driven collectively using smart vehicles is being studied.
Currently, group driving technology is technology in which a plurality of vehicles are driven while maintaining intervals of several meters from leading vehicles, and the group driving technology is receiving great attention as a solution capable of improving road efficiency and fuel efficiency.
Important technology needed for group driving technology is technology related to sensors such as radar sensors measuring distances between vehicles and wireless communication for sharing driving information between vehicles.
That is, group driving technology could also be seen as cooperative adaptive cruise control (ACC) driving in which a plurality of vehicles emulate driving of a leader vehicle by utilizing driving information of the leader vehicle in a conventional ACC function.
In this case, one of the vehicles performing the group driving drives as the leader vehicle, and there are one or more subordinate vehicles that drive subordinately to the leader vehicle behind the leader vehicle. The leader vehicle broadcasts its own vehicle status information to the subordinate vehicles as a periodical safety message, and the subordinate vehicles receiving the information drive along a driving path at constant intervals with reference to the driving information of the leader vehicle.
Messages transmitted and received through wireless communication devices installed in smart vehicles are largely classified as service data for vehicle infotainment, safety messages informing of periodical vehicle driving status information or an emergency status, and other control/management messages, etc. The general data services use a service channel, and the data related to vehicle safety and control/management, etc., uses a control channel that all vehicles use in common.
The safety messages are largely classified as safety messages (“general safety messages”) in which a vehicle transmits its own status information at a constant period, and messages (“emergency safety messages”) transmitted when a specific event occurs, and for example, the safety messages include a vehicle anti-collision support safety message, a road work zone alarm safety message, an emergency vehicle approach warning safety message, a road danger zone alarm safety message, an emergency rescue recovery alarm safety message, and an emergency disaster alarm safety message, etc.
Accordingly, since emergency safety messages such as emergency rescue recovery/disaster alarm safety messages have to be rapidly and reliably transmitted to nearby vehicles, reliability is required when transmitting and receiving emergency safety messages in an environment in which general safety messages are transmitted and received.
Accordingly, studies on transmission intensity and transmission periods, etc. of safety messages are progressing to enable stable and effective communications between vehicles driven in groups. Methods of controlling radio field intensity of a vehicle communication device that have been studied so far include a method of controlling radio field intensity based on a maximum/broadcasting message loading value, a method of controlling radio field intensity based on an occupancy rate of a wireless channel, and a method of controlling radio field intensity based on the number of target vehicles, etc. based on a radio field reception sensitivity ratio.
However, in current vehicle ad-hoc network (VANET) environments, studies related to radio field intensity control of vehicle communication devices have focused on methods of controlling the radio field intensity needed to control a data flow of an effective network when periodical messages are transmitted.
However, reliable transmission and reception of emergency safety messages such as disaster messages in an environment in which periodical messages are transmitted and received is not guaranteed. Particularly, the transmission and reception of periodical safety messages frequently occurs between vehicles driven in a group, and a solution is required because the transmission and reception of the periodical safety messages acts as an interference signal and obstructs the transmission and reception of emergency safety messages of not only the vehicle itself but also other nearby vehicles.